From the report: "Although the Internet Archive's Wayback Machine is the
largest and most well-known web archive, there have been a number of public web
archives that have emerged in the last several years. With varying resources,
audiences and collection development policies, these archives have varying
levels of overlap with each other. While individual archives can be measured in
terms of number of URIs, number of copies per URI, and intersection with other
archives, to date there has been no answer to the question - "How much of
the Web is archived?" We study the question by approximating the Web using
sample URIs from DMOZ, Delicious, Bitly, and search engine indexes; and,
counting the number of copies of the sample URIs exist in various public web
archives. Each sample set provides its own bias. The results from our sample
sets indicate that range from 35%-90% of the Web has at least one archived
copy, 17%-49% has between 2-5 copies, 1%-8% has 6-10 copies, and 8%-63% has
more than 10 copies in public web archives. The number of URI copies varies as
a function of time, but no more than 31.3% of URIs are archived more than once
per month." Read more
